1. Field of the Invention
The present invention relates in general to an apparatus for supporting and feeding a web material from a roll. More particularly, the present invention relates to a roll supporting and feeding apparatus that is preferably portable and that is capable of readily receiving a roll having a support core. The apparatus supports the web material in a roll for feeding to a utilization means that draws the webbed material thereto.
2. Background discussion
There are several types of prior art role feeding machines. Many of these machines are of relatively complicated structure and these machines tend to generally be relatively expensive. These prior art machines also tend to be relatively limited in application and are not readily usable for universal applications.
One of the significant drawbacks associated with prior art roll feeding machines relates to the manner in which the roll is supported in the machine. The prior art machines employ a roll core shaft. These shafts represent an extra component that must be assembled in order to handle the roll. The core shafts are very heavy and are easily damaged if dropped. They are also expensive to replace or repair. These mechanical core shafts tend to get their tightened head worn out from the constant use of a tool. With respect to the air filled core shafts they require the use of clean air. They also suffer from rupture of or leakage from their bladder. Moreover, in the use of these core shafts, the shafts are quite apt to get stuck in the cores. They provide cleats that dig into the cardboard cores and thus are difficult to dislodge. This is in particular one of the major problems with the air operated core shafts because they depend on springs to retract them. When the shaft is stuck it has to be driven out causing further destruction of the shaft.
With the previous use of core shafts, the loading of a new roll requires extra time to remove the shaft from the old roll and replace it with a new one, or alternatively, spare shafts must be employed. The spare shaft is a safety problem because it tends to be in the way in the general work area. A further problem associated with the use of core shafts is that it assumes that the core is in undamaged condition and of essentially perfect shape to accept the shaft. If a core is damaged at any place along the length thereof then there is extreme difficulty in properly inserting the core shaft into the core.
Even once the core shaft is inserted in the roll core, the shaft engagement into the machine in these prior art machines furthermore requires intense operator attention. If a shaft is mounted improperly and gets out of its socket then the heavy roll may dangerously roll across the floor. Also, the shaft mounted roll requires the roll to be put precisely into the center of the shaft. Otherwise the paper runs off-center.
Accordingly, it is an object of the present invention to provide an improved means for roll support, one that in particular, does not require the use of core shafts and one that provides for essentially automatic roll alignment in the machine.
The prior art roll machines also provide means for speed matching with the machine into which the roll is being fed. These prior art machines rely upon a weighted bar or dancer that rides on the web and is pivoted to hold the web in place.
A sensor is then employed to detect the position of the weight (dancer). This weighted bar approach may be adequate for some applications. However, when used, in particular, with say impact printers or bursters, which have widely varying speeds, then this prior art arrangement is quite inadequate. The weighted bar device puts substantial strain on the pin feed holes. Even with the weight counterbalanced, the speed changes cause inertia forces that distort the pin feed holes. This tension complicates the paper steering operation. This requires exact alignment and tram.
Accordingly, another object of the present invention is to provide an improved apparatus for supporting and feeding web material from a roll in which there is provided improved speed matching with the utilization machine. The technique of the present invention preferably eliminates the use of a weight bar and thus does not require any special alignment.
Still another object of the present invention is to provide an improved speed matching control for a roll feed machine that employs an analog form of detection including a position detector means responsive to the position of a gravity loop of web material.
A further object of the present invention is to provide a sensor in accordance with the preceeding object which is preferably a noncontact sound sensor having no moving parts that could wear out.
Another problem associated with prior art machines is the "telescoping" of rolls. The prior art machines have several problems with telescoping, especially with narrow width webs and with rolls smaller than two feet in diameter. The propensity of these prior art machines to telescope these small diameter rolls leads to a substantial web material waste. One prior art machine employes a complex controller that accelerates and stops the roll by a gear on the shaft. This has several problems. The shaft has to be in good condition or it looses its grip and therefore its control on the roll. The shaft force has to have a ten to one variation to provide uniform force on the surface of the web as the radius changes as the roll runs down. This is complicated and not particularly accurate. With this prior art machine it is particularly troublesome when starting and stopping because the inertia is a complex function of the radius which changes as the roll runs down. With this prior art machine the starting and stopping action on the core can rip the first layer of paper after the core. This happens most often on a new roll. This means that a large roll is ruined because it is slipping in the layers of paper behind the cardboard core. The use of a shaft that is poorly installed or damaged can ream out the core inside and ruin the roll. If the shaft is not properly expanded by the operator, the roll of paper may get out of control and dump substantial amounts of waste on the floor.
Accordingly, a further object of the present invention is to provide an improved drive technique for a roll feeding machine and one which in particular eliminates the aforementioned problem of the "telescoping" of the roll.
Still another object of the present is to provide an improved apparatus for supporting and feeding web material from the roll in which the apparatus is relatively light, drives the roll without marking the roll, is easy to service and maintain, and is of simplified construction particularly as it relates to setting up a roll for feeding.